IPsec: Add DPD configuration options to advanced settings.
IPsec: Fix and enhance DPD configuration.

Also the action option has now moved to the advanced settings
page and the design has been improved.
IPsec: Allow to disable DPD.
IPsec: Move IKE protocol option to advanced settings page.
IPsec: Make connection configuration more pleasant for the eye.
Update translations.
Merge remote-tracking branch 'ms/ipsec-dpd' into fifteen